US6855454B2 - Electrochemical cell having venting current collector and seal assembly - Google Patents

Abstract

A low profile collector and seal assembly for sealing the open end of a container of an electrochemical cell and providing venting of pressurized gases. An electrochemical cell has a can with a closed bottom end and an open top end, positive and negative electrodes disposed in the can, and a collector and seal assembly disposed in the open top end of the can for closing the open top end of the can. The collector and seal assembly includes a current collector and an annular seal that move relative to each other from a sealed position to a vented position when the internal cell pressure reaches a pressure threshold to vent pressurized gases.

Description

BACKGROUND OF THE INVENTION

The present invention generally relates to electrochemical cells (i.e., batteries) and, more particularly, to a current collector and seal assembly for sealing the open end of a cell container and providing pressure relief for venting gases when exposed to excessive pressure.

Conventional alkaline electrochemical cells generally include a steel cylindrical can having a positive electrode, referred to as the cathode, which commonly comprises manganese dioxide as the active material. The electrochemical cell also includes a negative electrode, referred to as the anode, which commonly comprises zinc powder as the active material. In bobbin-type cells, the cathode is typically formed against the interior surface of the steel can, while the anode is generally centrally disposed in the can. A separator is located between the anode and the cathode, and an alkaline electrolyte solution simultaneously contacts the anode, the cathode, and the separator. A conductive current collector is inserted into the anode active material to provide an electrical path to a negative outer terminal. An annular polymeric (e.g., nylon) seal provides closure to the open end of the steel can to seal the active electrochemical materials in the sealed volume of the can. An inner cover radially supports the seal. The current collector, inner cover, and seal are typically assembled together to form a collector and seal assembly.

Cylindrical alkaline cells are typically sealed closed by placing the collector and seal assembly in the open end of the steel can and crimping the upper end of the can inwardly and over the outer periphery of the seal to compress the seal. However, electrochemical cells commonly employ electrochemically active materials, such as zinc, which generate hydrogen gas, particularly when subjected to abusive discharge conditions, such as battery reversal, as well as during storage, and sometimes during or following service use. When the can is sealed closed, excessive build-up of high pressure gases within the sealed can may force the crimped closure open and cause damage to the cell and/or the device in which the cell is employed.

One approach to avoiding a potentially excessive build-up of pressure in a cell has been to employ a resealable valve system that periodically releases excessive pressurized gases from within the active cell volume. However, the continued periodic release of pressurized gases may, in some situations, permit the release of electrolyte solution containing salts or other particulate matter, which may foul the resealable valve, and such systems generally require additional costly components. Another approach to avoiding excessive build-up of internal pressure involves employing a sealed membrane that is intended to blow out when exposed to excessive pressure either by puncture or rupture of the membrane itself. A puncture mechanism, such as a spiked member, may be employed to punch a hole in the sealed membrane once the internal pressure reaches a predetermined amount.

A further approach to venting excessively pressurized gases has included the use of a vent formed in the seal which is intended to rupture upon experiencing an excessive pressure build-up in the sealed interval volume of the cell. As an example, U.S. Pat. No. 5,667,912 discloses a current collector assembly having a seal with a thinned portion formed in the seal diaphragm axisymmetrical about a rotation of the central longitudinal axis of the cell. The thinned portion of the seal is intended to shear when the internal pressure exceeds a predetermined pressure threshold, to thereby create a pressure relief vent passage.

While the aforementioned conventional approaches have served to vent high pressure gases in commercial cells, many of these approaches involve complex seal designs which consume a significant amount of volume. Increased collector and seal assembly volume generally results in reduced internal volume available for electrochemically active materials, thus limiting the service performance capability of the cell. Additionally, some conventional venting seals exhibit poor leakage performance. Further, the venting pressure is generally limited in conventional rupture type venting seals due to the difficulty in injection molding the thinned portion of the seal. Accordingly, it is therefore desirable to provide for an electrochemical cell having a simplified, low profile collector and seal assembly that effectively vents pressurized gases at a predetermined pressure, is capable of achieving lower vent pressures, and exhibits enhanced leakage performance.

SUMMARY OF THE INVENTION

The present invention improves the protective safeguards of an electrochemical cell with an easy-to-manufacture and low profile collector and seal assembly for sealing the open end of an electrochemical cell container and providing controlled venting of pressurized gases. To achieve this and other advantages, and in accordance with the purpose of the invention as embodied and described herein, the present invention provides for an electrochemical cell having a container with a bottom end and an open top end, and positive and negative electrodes and an electrolyte disposed in the container. The cell further includes a collector and seal assembly disposed in the open top end of the container for closing the open top end of the container. The collector and seal assembly includes a current collector disposed in contact with one of the positive and negative electrodes, and a seal member having an opening defined by an upstanding wall. The current collector is interference fit within the opening in the seal member such that the seal member is in sealing engagement with a shaft of the current collector. The current collector and the upstanding wall of the seal member are axially (i.e., parallel to a longitudinal axis of the cell) moveable relative to each other upon experiencing a predetermined pressure to move from a sealed position to a vent position so as to provide a pressure relief passage to vent pressurized gases.

According to one aspect of the invention, the current collector has a shaft extending through an opening defined by an upstanding wall in a central hub of the seal member, and the current collector moves within the opening from a sealed position to a vent position to provide a pressure relief passage. According to another aspect of the invention, the current collector has a shaft extending through a central opening defined by an upstanding wall in the seal member and sealingly engaged with the upstanding wall of the seal member forming the central opening, and the central hub of the seal member moves on the shaft from a sealed position to a vent position to provide a pressure relief passage.

These and other features, advantages and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims and appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a cutaway view of an electrochemical cell having a collector and seal assembly according to a first embodiment of the present invention, shown in a sealed (non-vented) position;

FIG. 2 is a cutaway view of the electrochemical cell ofFIG. 1 with the collector and seal assembly shown in a vented position;

FIG. 3 is a partial cutaway view of an electrochemical cell having a collector and seal assembly according to a second embodiment of the present invention, shown in a sealed (non-vented) position;

FIG. 4 is a partial cutaway view of the electrochemical cell ofFIG. 3 with the collector and seal assembly shown in a vented position;

FIG. 5 is a partial cutaway view of an electrochemical cell having a collector and seal assembly according to a third embodiment of the present invention, shown in a sealed (non-vented) position;

FIG. 6 is a partial cutaway view of the electrochemical cell ofFIG. 5 with the collector and seal assembly shown in a vented position;

FIG. 7 is an elevated perspective view of the collector connector shown in the embodiment ofFIG. 5;

FIG. 8 is a partial cutaway view of an electrochemical cell having a collector and seal assembly according to a fourth embodiment of the present invention, shown in a sealed (non-vented) position;

FIG. 9 is a partial cutaway view of the electrochemical cell ofFIG. 8 with the collector and seal assembly shown in a vented position;

FIG. 10 is a partial cutaway view of the electrochemical cell ofFIG. 8 with the collector and seal assembly partially retracted from the vented position;

FIG. 11 is an elevated perspective view of the annular seal member shown in the embodiment ofFIG. 8;

FIG. 12 is a partial cutaway view of an electrochemical cell having a collector and seal assembly according to a fifth embodiment of the present invention, shown in a sealed (non-vented) position; and

FIG. 13 is a partial cutaway view of the electrochemical cell ofFIG. 12 with the collector and seal assembly shown in a vented position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring toFIG. 1, a cylindrical alkalineelectrochemical cell10 is shown having a collector andseal assembly30 according to a first embodiment of the present invention.Electrochemical cell10 includes a cylindrical steel can12 having a closedbottom end14, an opentop end16, and a cylindrical side wall extending between the bottom and top ends. The closedbottom end14 of can12 has a positive cover welded or otherwise attached thereto and formed of plated steel, with aprotruding nubbin18 at its center region, which forms the positive contact terminal ofcell10. Assembled to theopen top end16 of steel can12 is the collector andseal assembly30, and an outernegative cover50, preferably formed of plated steel, which forms the negative contact terminal ofcell10. A metalized,plastic film label20 is formed about the exterior surface of steel can12, except for the ends of steel can12.Film label20 is formed over the peripheral edge of the positive cover and may extend partially over the peripheral edge of thenegative cover50.

Apositive electrode22, also referred to herein as the cathode, is formed about the interior surface of steel can12. According to one example, thecathode22 is formed of a mixture of manganese dioxide, graphite, potassium hydroxide solution, and additives. Aseparator24, which is preferably formed of a non-woven fabric that prevents migration of any solid particles in the cell, is disposed about the interior surface ofcathode22. Anegative electrode26, also referred to herein as theanode26, is disposed with an electrolyte inside theseparator24 and in contact with acurrent collector32. The electrolyte may include an alkaline electrolyte containing potassium hydroxide (KOH). According to one example, theanode26 is formed of zinc powder, a gelling agent, and additives. The manganese dioxide and zinc employed in thecathode22 andanode26, respectively, are electrochemically active materials. Accordingly, thecathode22 is configured as the cell's positive electrode, and theanode26 is configured as the cell's negative electrode.

Thecurrent collector32 contacts the outernegative cover50 which forms the negative contact terminal ofcell10. Thecurrent collector32 is generally configured in the shape of a nail having an elongatedcylindrical shaft34, a truncatedconical tip35 at the lower end, and anenlarged head36 at the upper end. Theelongated shaft34 is disposed in contact with theanode26 and, in this embodiment, has a substantially uniform diameter. Thecurrent collector32 is connected to the outernegative terminal50 via a coiledconductive connector38 that is compressible. The coiledconnector38 may be welded to the bottom surface of outernegative cover50 and/or to the upper surface ofenlarged head36 ofcurrent collector32, or alternately may be held in contact therewith via pressure contact.Current collector32 andconnector38 serve as an electrical current path to provide the negative polarity at the outernegative cover50.

Anannular polymeric seal40 is disposed in the open end of steel can12 to prevent leakage of electrochemically active cell materials contained in steel can12.Polymeric seal40 may comprise a synthetic thermoplastic resin such as nylon. Alternate materials forseal40 may include polypropylene, such as Noryl® Extend which is commercially available from General Electric Company, and other materials that would be recognized as suitable forseal40.

Seal40 has acentral hub42 with an inner upstandingcylindrical wall44 defining a central opening (i.e., aperture) for receiving thecurrent collector32.Hub42 is generally defined as the central portion ofseal40 containingupstanding wall44 which is compressed against thecurrent collector32. Theenlarged head36 ofcurrent collector32 is generally oversized for the hub opening, and thus theseal40 is compressed against thecurrent collector32 to form an interference fit engagement with the innerupstanding wall44 defining the hub opening. Theupstanding wall44 ofcentral hub42 is configured to sealingly engage theenlarged head36 ofcurrent collector32 when in a sealed (non-vented) position. Thecentral hub42 also has anupper edge43 shown inFIG. 1 formed over the upper peripheral surface ofenlarged head36 to further resist upward movement ofcurrent collector32. Aninner cover46, which is preferably formed of a rigid metal, is provided to increase the rigidity and support the radial compression ofannular seal40, thereby improving the sealing effectiveness. Theinner cover46 is configured to contact an outer upstanding wall ofcentral hub42 and an upstanding wall at the outerperipheral section45 ofseal40. While an oversizedcurrent collector32 and aninner cover46 are used to compress theseal40 against thecurrent collector32, other compression techniques such as compression rings may be employed to provide a sealed interference fit engagement between thecurrent collector32 andseal40. Theseal40,inner cover46, and outernegative cover50 provide a low profile closure to theopen end16 ofcan12. In addition, the outernegative cover50 also includes one ormore vent openings52 that serve to expose the non-sealed volume ofcell10 to the surrounding outside atmosphere.Vent openings52 serve to vent pressure build-up released from within thecell10 to the outside atmosphere once the collector and sealassembly30 vents.

Together, thecurrent collector32,annular seal40, andinner cover46 form the collector and sealassembly30 which may be assembled together and inserted as a unit into theopen end16 of steel can12. The assembly of the collector and sealassembly30 and closure of theopen end16 ofcan12 include disposing theannular polymeric seal40 in theopen end16 of thecan12, which may have a flared opening or a bead formed radially inward on the inner wall of thecan12, and crimping the upper end of thecan12 inwardly and over theouter periphery45 of theseal40 to compress theseal40 against theinner cover46. It should also be appreciated that the outernegative cover50 is electrically insulated from the steel can12 by way of annularpolymeric seal40.

According to the present invention, the current collector and sealassembly30 seals closed theopen end16 ofcan12, provides an electrical current path to the outernegative terminal50, and further acts a pressure relief mechanism when exposed to an excessive pressure differential. The collector and sealassembly30 is designed to release pressurized gases from within the sealed active volume ofcell10 when theassembly30 is exposed to a predetermined pressure differential. The pressure differential is the difference between the internal pressure below theseal40 and the atmospheric pressure above theseal40. The pressurized gas venting is generally achieved by relative axial (i.e., parallel to a longitudinal axis of the current collector32) movement between thecurrent collector32 and annularpolymeric seal40. The pressurized gases released from the internalvolume exit cell10 viaopenings52 provided in the outernegative cover50.

According to the first embodiment,current collector32 is interference fit and sealingly engaged withannular seal40 while in the sealed (non-vented) position as shown in FIG.1. The sealing engagement is formed between thehead36 ofcollector32 and the upstandingwall forming hub42 ofseal40. As the pressure increases within the sealed volume, which is generally below the bottom surface ofseal40, such as may occur during an abusive condition, the internal pressure applies a force on thecurrent collector32 which will tend to urge thecurrent collector32 upward and out of sealing engagement withannular seal40. When the pressure differential of the internal sealed volume, as compared to the outer atmospheric pressure, exceeds a predetermined pressure threshold, thecurrent collector32 is forced free from the sealing engagement with thehub42 ofseal40 and moves to a vented position as shown in FIG.2. The forced disengagement causes the upper foldedend43 ofhub42 to bend upward to allow upward movement ofcollector head36. When this occurs, thecurrent collector32 is forced upward relative to theentire hub42 ofseal40 which remains substantially fixed in place. It should be appreciated that thehub42 ofseal40 generally will not move upward more than a small distance compared to the movement of thecurrent collector32, and thus is considered substantially fixed. In the vented position, apressure relief passage48 is provided between theseal hub42 and thecurrent collector32 to allow for the release of pressurized gases from within the internal volume ofcell10. In addition, when thecurrent collector32 moves from the sealed position to the vented position, the coiledconductive connector38 is compressed between the top surface of thecurrent collector head36 and the bottom surface of outernegative terminal50. When compressed, coiledconductive connector38 may apply an opposing spring bias force downward such that when the pressure differential decreases to a reduced pressure threshold, thecurrent collector32 may be biased downward so that thecollector head36 sealingly engages theseal hub42. In the event that the internal pressure increases after resealing, thecurrent collector32 will again be forced upward to open thepressure relief passage48 to further vent pressurized gases.

Anelectrochemical cell10′ is shown inFIGS. 3 and 4 having an alternatively configuredcurrent collector32′ as part of a collector and sealassembly30′. Thecurrent collector32′ includes amain shaft34 that extends to the uppermost end, without the enlarged head portion as discussed above. Instead,current collector32′ includes a plurality of longitudinal flutes (i.e., channels)62 extending upward toward the uppermost end. It is preferred that the inner upstanding wall forming the hub ofseal40 be no higher than the length of theflutes62. Thecurrent collector32′ is positioned in the sealed position such that the plurality offlutes62 are located belowseal40, as shown in FIG.3. Thecurrent collector32′ is interference fit and sealingly engaged with the inner upstanding wall forming the opening inhub42 ofseal40. During the venting operation, thecurrent collector32′ is forced upward relative to theentire hub42 ofseal40 which remains substantially fixed in place as discussed above. When a sufficient internal pressure forces thecurrent collector32′ upward, thelongitudinal flutes62 provide a pressure relief passage around the inner upstanding wall forming the hub ofseal40 as shown in FIG.4. While a plurality offlutes62 is shown, it should be appreciated that any one or more flutes may be employed according to this embodiment.

Referring toFIGS. 5-7, anelectrochemical cell10″, according to a third embodiment, is shown similar tocell10 ofFIG. 1, except having an alternatively configuredconductive connector38′ for providing an electrical current path between thecurrent collector32 and outernegative cover50.Conductive connector38′ is shown inFIG. 7 generally configured as a bowl-shaped disk made of conductive material, such as steel. With particular reference toFIG. 5, the upper outer peripheral rim engages the bottom surface of outernegative cover50, while the bottom dome contacts the upper surface ofcurrent collector head36.Conductive connector38′ preferably provides a downward biased force to thecurrent collector32 so as to maintain a sealed engagement with theannular seal40 while in the sealed (non-vented) position. When the sealed internal pressure reaches a predetermined pressure, relative to the atmospheric pressure, thecurrent collector32 moves to a vented position, as shown inFIG. 6, during which theconductive connector38′ compresses vertically to allow formation of thepressure relief passage48. Once the internal pressure decreases to a lower pressure, theconductive connector38′ may force thecurrent collector32 back into sealing engagement withseal40, as discussed above in connection with the first embodiment.

Anelectrochemical cell110 is shown inFIGS. 8-10 having a collector and sealassembly130 according to a fourth embodiment of the present invention.Electrochemical cell110 includes asteel can12,label20,cathode22,separator24, and ananode26, as described above in connection with the first and second embodiments. According to the fourth embodiment,electrochemical cell110 includes collector and sealassembly130 for sealing closed theopen end16 ofcan12, providing an electrical current path to an outernegative cover150, and providing a pressure relief mechanism to vent pressurized gases. The collector and sealassembly130 includes anannular polymeric seal140 and acurrent collector132. The current collector and sealassembly130 of the fourth embodiment does not require an inner cover as used in the collector and seal assemblies of the first, second, and third embodiments described above.

Thecurrent collector132 includes a lowercylindrical shaft134, anenlarged diameter step139, a reduced diametercylindrical shaft137, and anenlarged head136 at the upper end. Thelower shaft134 ofcurrent collector132 extends into andcontacts anode26. The reduceddiameter shaft137 is located between theenlarged diameter step139 andenlarged head136, and preferably has a diameter less than the diameter of thelower shaft134. The upper surface ofenlarged head136 may be welded to, or in pressure contact with, outernegative cover150.

Theannular seal140 includes acentral hub142 having an innerupstanding wall144 defining a central opening for receiving thecurrent collector132. The outerperipheral portion145 ofseal140 forms a sealed closure against thecan12 and provides dielectric isolation between steel can12 and outernegative cover150. It should be appreciated that theopen end16 of thecan12,seal140, andouter cover150 are crimped so as to compress theseal140 and provide a sealed closure. Thecurrent collector132 is interference fit within the opening formed by innerupstanding wall144 ofseal140. The innerupstanding wall144 ofseal140 is compressed againstcurrent collector132 and sealingly engages thecurrent collector132 when in a sealed (non-vented) position as shown in FIG.8.

Referring toFIG. 9, theelectrochemical cell110 is shown with the collector and sealassembly130 in a vented position. When the internal pressure within the sealed volume ofelectrochemical cell110 exceeds a predetermined pressure threshold, relative to the atmospheric pressure, thecentral hub142 ofseal140 is forced upward due to the differential pressure applied to theseal140. When the pressure differential exceeds the pressure threshold,hub142 is forced over theenlarged diameter step139 to a position abovestep139 to provide apressure relief passage148 betweenseal140 andcurrent collector132. When this occurs, theentire hub142 is forced upward relative to thecurrent collector132 which remains substantially fixed in place. It should be appreciated that thecurrent collector132 may move upward a small distance, however, it is a relatively small distance compared to the movement of theentire hub142 ofseal140. By providing the reduceddiameter section137, thepressure relief path148 is provided without allowing resealing betweenreduced diameter section137 andseal140.Outer cover150 includes one ormore vent openings152 to vent pressure build-up released from withincell110 to the outside atmosphere.

Once the pressure differential has decreased to a lower pressure, thehub142 ofseal140 may slide downwardly (retract) back into sealing engagement on the upper side of theenlarged diameter step139 as shown in FIG.10.Central hub142 ofseal140 has a shaped surface indentation (bevel)141 provided in the lower section ofupstanding wall144 which substantially conforms to the shape of the upper surface ofenlarged diameter step139. Upon retracting downward, theseal140 may again sealingly engagecurrent collector132 to prevent further discharge of gases and other material. It should be appreciated that upon the pressure differential increasing, additional venting of pressurized gases may occur.

With particular reference toFIG. 11, theannular polymeric seal140 is shown having a plurality ofchannels160 formed in the upper surface. It should be appreciated that by employing one or more standoff members, such aschannels160, in the upper surface ofseal140, thechannels160 provide a vent path to prevent resealing ofseal140 withcurrent collector132 when in the vent position. It should also be appreciated that as an alternative to channels, other standoff members, such as ribs or other surface protrusions, may be provided either on the upper surface ofseal140 or on the surface ofcurrent collector130 to prevent resealing during the venting operation. Examples of anti-resealing assemblies are disclosed in U.S. Application Ser. No. 09/300,413, filed Apr. 27, 1999, now U.S. Pat. No. 6,270,919, issued Aug. 7, 2001, entitled “ELECTROCHEMICAL CELL HAVING LOW PROFILE SEAL ASSEMBLY WITH ANTI-RESEALING VENT,” which is hereby incorporated by reference.

Referring toFIGS. 12 and 13, anelectrochemical cell110′ is illustrated having a collector and sealassembly130′ according to a fifth embodiment of the present invention. Theelectrochemical cell110 likewise includes asteel can12,label20,cathode22,separator24,anode26, and other components as discussed above. The collector and sealassembly130′ of the fifth embodiment includes acurrent collector132′ having alower shaft134, anenlarged diameter step139, and a plurality of longitudinal flutes (i.e., channels)162 extending from theenlarged diameter step139 upward toward theenlarged head136. Thecurrent collector132′ is likewise connected to the outernegative cover150. The plurality offlutes162 providepressure relief passages148 for releasing pressurized gases from the internal volume of thecell110′ in a controlled operation. In the non-vented position, shown inFIG. 12, thehub142 ofseal140 provides sealing engagement betweenupstanding walls144 and each ofshaft134 and step139 ofcurrent collector132′. Theshaft134 ofcurrent collector132′ is interference fit within the opening formed by the inner walls ofhub142 ofseal140. When the internal pressure within the sealed volume ofcell110′ increases beyond a predetermined pressure threshold, thecentral hub142 slides upward alongcurrent collector132′ until one or morepressure relief passages148 are provided throughflutes162 to release the high pressure gases from within the sealed volume, as shown in FIG.13. It should be appreciated that thecurrent collector132′ remains substantially fixed, relative to the movement of theentire hub142 ofseal140, as discussed above. By providing a plurality offlutes162 to serve as the pressure relief passages, a controlled low pressure release of gases may be achieved according to this embodiment.

Theseal member140 is made of a polymeric material, such as Noryl® Extend which is commercially available from General Electric Company of Selkirk, N.Y. Noryl® Extend is a polypropylene matrix having polyethylene therein, which acts as a polymer stiffener. Noryl® Extend provides low moisture absorption, will not hydrolyze in the presence of KOH, and has very low stress relaxation. These characteristics allow the seal design of the present invention to be feasible, whereas use of a material such as nylon for theseal140 of the present invention would require the use of a support. This is due to nylon cracking in the presence of KOH coupled with stress on the seal (in the hoop direction) due to the nail vent design.

It should be appreciated that, while Noryl® Extend is a preferred material forseal140 that resists cracking, particularly in the central hub, other seal materials could be used. For example, theseal members40 and140 may include nylon, such as Zytel® 101F, which is commercially available from E. I. duPont deNemours and Co. Inc.Seal members40 and140 can be integrally formed using a conventional injection molding process. In addition, the bottom surface ofseal members40 and140 may be coated with a layer of asphalt (not shown) or other suitable material to prevent chemical degradation of the seal member due to the presence of electrolyte.

While the various embodiments described herein provide a pressure relief passage achieved by relative axial movement between a collector and a seal, it should be appreciated that other vent passages may be provided. For example, the relative movement between the seal and collector may be designed to cause the seal hub to split open, thereby further creating a pressure relief passage through the split opening.

Accordingly, the present invention advantageously provides collector and seal assemblies for sealing the open end of an electrochemical cell and realizing a controlled venting operation to vent high pressure gases, particularly when the cell is subjected to an abusive condition. The collector and seal assemblies of the present invention each offer a simplified seal design in a low profile assembly which results in greater volume available for active battery components. The seals of the present invention are easy to mold, since no conventional thin sections are required for the vent diaphragm. In addition, a wide range of vent pressures is achievable by adjusting the nail step diameter in its relation to the seal hub inside diameter, seal hub outside diameter, and nail diameter below the enlarged diameter step. The venting rate can easily be adjusted with the collector and seal assemblies of the present application. Generally, the pressurized gases in the cell will escape faster if the diameter difference between the vent region of the nail and seal is made greater, and if the vent channel cross section area on top of the seal is increased. Likewise, the seal can be designed to vent slower to create less release spray if the diameter clearance is decreased or the vent channel is decreased. By providing the seal such that it can flex back to a non-vent position, reduced or prevented leakage of electrolyte after the seal has vented can be achieved. Further, it should be appreciated that the collector and seal assemblies of the present invention employ fewer parts and less volume than conventional seal assemblies.

While the collector and seal assemblies have been described herein in connection with a cylindrical bobbin-type electrochemical cell, it should be appreciated that the invention concepts are likewise applicable to various other cell configurations including jelly roll cells, prismatic cells, cells employing multiple anodes and multiple current collectors and cells in which the cans and current collectors are electrically connected to the negative and positive electrodes, respectively. Additionally, it should also be appreciated that the collector and seal assemblies described herein may be sealed closed against the steel can using various different can closures.

It will be understood by those who practice the invention and those skilled in the art, that various modifications and improvements may be made to the invention without departing from the spirit of the disclosed concepts. The scope of protection afforded is to be determined by the claims and by the breadth of interpretation allowed by law.

Claims (23)

1. An electrochemical cell comprising:

a container having a bottom end and an open top end;

a positive electrode disposed in said container;

a negative electrode disposed in said container;

a seal member disposed in the open top end of said container for closing the open top end of said container, said seal member having an opening defined by an upstanding wall; and

a current collector having a shaft extending through the opening in said seal member and contacting one of the positive and negative electrodes, wherein the current collector is interference fit within the opening such that the upstanding wall of the seal member sealingly engages the shaft of the current collector when in a sealed position, and the upstanding wall of the seal member is axially movable along the shaft of the current collector to a vent position upon experiencing a predetermined pressure so as to provide a pressure relief passage between the upstanding wall of the seal member and the current collector to vent pressurized gases; wherein

the upstanding wall of the seal member is retained in the scaled position by an enlarged diameter step provided on the shaft of the current collector, and the upstanding wall of the seal member is forced to move over the enlarged diameter step to the vent position.

2. The electrochemical cell as defined inclaim 1, wherein said seal member and current collector form a collector and seal assembly.

3. The electrochemical cell as defined inclaim 1, wherein said current collector includes a shaft having a first diameter sealingly engaging the upstanding wall of the seal member in the sealed position, and a second reduced diameter shaft that has a diameter less than the first diameter, wherein the upstanding wall of the seal member is forced to move towards the second reduced diameter to provide the pressure relief passage when the seal member is in the vent position.

4. The electrochemical cell as defined inclaim 1, wherein said current collector has one or more flutes formed therein for providing the pressure relief passage when in the vent position.

5. The electrochemical cell as defined inclaim 1, wherein said seal member includes a vent path provided on the top surface of the seal member to prevent resealing of the current collector and seal member when in the vent position.

6. The electrochemical cell as defined inclaim 1, wherein said seal member comprises polypropylene.

7. The electrochemical cell as defined inclaim 1, wherein said seal member comprises polymeric material.

8. The electrochemical cell as defined inclaim 1, wherein said collector assembly and seal member sealingly engage each other following initial pressure venting.

9. The electrochemical cell as defined inclaim 1 further comprising an alkaline electrolyte.

10. An electrochemical cell comprising:

a container having a bottom end and an open top end;

a positive electrode disposed in said container;

a negative electrode disposed in said container;

a seal member disposed in the open top end of said container for closing the open top end of said container, said seal member having a central hub and an opening defined by an upstanding wall formed in the central hub; and

a current collector having a shaft extending through the opening of said seal member and contacting one of the positive and negative electrodes, wherein the current collector is interference fit within the opening such that the seal member sealingly engages the shaft of the current collector when in a sealed position, and the central hub of the seal member is forced to move along the shaft of the current collection from a sealed position to a vent position upon experiencing a predetermined pressure so as to provide a pressure relief passage between the upstanding well of the seal member and the current collector to vent pressurized gases; wherein

the upstanding wall of the seal member is retained in the sealed position by an enlarged diameter step provided on the shaft of the current collector, and the upstanding wall of the seal member is forced to move over the enlarged diameter step to the vent position.

11. The electrochemical cell as defined inclaim 10, wherein the current collector includes a shaft having a first diameter sealingly engaging the upstanding wall of the seal member in the sealed position, and a second reduced diameter shaft that has a diameter less than the first diameter, wherein the seal member is forced to move towards the second reduced diameter shaft to provide the pressure relief passage when the seal member is in the vent position.

12. The electrochemical cell as defined inclaim 10, wherein the current collector include one or more flutes therein for providing the pressure relief passage when in the vent position.

13. The electrochemical cell as defined inclaim 10, wherein said seal member includes a vent path provided on the top surface of the seal member to prevent resealing of the current collector and seal member when in the vent position.

14. The electrochemical cell as defined inclaim 10, wherein the seal member and current collector from a collector and seal assembly.

15. The electrochemical cell as definedclaim 10 further comprising an alkaline electrolyte.

16. The electrochemical cell as defined inclaim 10, wherein said seal member comprises polypropylene.

17. A collector and seal assembly for sealing the open end of an electrochemical cell container, said collector and seal assembly comprising:

a seal member adapted to be disposed in an open end of a container to provide a sealed closure to the open end of the container, said seal member having an opening defined by an upstanding wall; and

a current collector having a shaft extending through the opening in said seal member, wherein the current collector is interference fit within the opening such that the upstanding wall of the seal member sealingly engages the shaft of the current collector when in a sealed position, and the seal member is forced to move axially relative to the current collector to move to a vent position upon experiencing a predetermined pressure so as to provide a pressure relief passage between the upstanding wall of the seal member and the current collector to vent pressurized gases; wherein

the upstanding wall of the seal member is retained in the sealed position by an enlarged diameter step provided on the shaft of the current collector, and the upstanding wall of the seal member is forced to move over the enlarged diameter step to the vent position.

18. The collector and seal assembly as defined inclaim 17, wherein said current collector includes a shaft having a first diameter sealingly engaging the upstanding inner wall of the seal member in the sealed position, and a second reduced diameter shaft that has a diameter less than the first diameter, wherein the upstanding wall of the seal member is forced to move towards the second reduced diameter shaft to provide the pressure relief passage when the seal member is in the vent position.

19. The collector and seal assembly as defined inclaim 17, wherein said current collector includes one or more flutes formed therein for providing the pressure relief passage when in the vent position.

20. The collector and seal assembly as defined inclaim 17, wherein said seal member includes a vent path provided on the top surface of the seal member to prevent resealing of the current collector and seal member when in the vent position.

21. The collector and seal assembly as defined inclaim 17, wherein said seal member comprises polypropylene.

22. The collector and seal assembly as defined inclaim 17, wherein said seal member comprises polymeric material.

23. The collector and seal assembly as defined inclaim 17, wherein said collector assembly and seal member sealingly engage each other following initial pressure venting.

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